Moving ramp

ABSTRACT

Moving ramp intended e.g. for transportation of people, comprising plates (10) supported by wheels, which are guided for movement at an upper level to form the loaded part of the moving ramp, and at a lower level which is substantially parallel with the upper level, to form the returning part of the moving ramp, adjacent plates in each part being close to each other. Stationary guides (16, 17) are provided as upper and lower runway tracks for the wheeled plates. The plates at the edges thereof are pivotally connected to endless chains (14) at one end of the plates the chains extending along the parts to be driven in one direction in the upper part and in the opposite direction in the lower part, a sprocket wheel (15) being provided for each chain (14) at each end thereof defining the distance between the parts. The other end of the plates is free for angular adjustment. For lowering and raising, respectively, the plates by engagement with the end of the plates which can be freely adjusted angularly, a rotating element (20, 22) driven synchronously with the sprocket wheel is provided at each end of the moving ramp. A number of drive stations for the endless chains are distributed along the length of the chains at least in the upper part thereof.

BACKGROUND OF THE INVENTION

The invention relates to a moving ramp intended e.g. for transportationof people, comprising plates supported by wheels, which are guided formovement at an upper level to form the loaded part of the moving ramp,and at a lower level which is substantially parallel with the upperlevel, to form the returning part of the moving ramp adjacent plates ineach part being close to each other, wherein stationary guides areprovided as upper and lower runway tracks for the wheeled plates, theplates at the edges thereof are pivotally connected to endless chains atone end of the plates said chains extending along the parts to be drivenin one direction in the upper part and in the opposite direction in thelower part, the other end of the plates being free for angularadjustment in cooperation with guides at the ends of the moving ramp tolower and raise, respectively, the plates by vertical displacementthereof in a substantially horizontal position one at the time from onepart to the other.

U.S. Pat. No. 3,447,666 describes a moving ramp of this kind wherein thechains move in a substantially rectangular path, turning sprockets beingprovided at the four corners of the rectangle, and wherein a transitionportion of each chain between the upper part and the lower part beingutilized to transfer the end of the plates which is connected to thechain, from the upper part to the lower part, and vice versa. For thetransfer of the free end of the plates there is provided at each end ofthe moving ramp endless auxiliary chains which are also guided in arectangular path over turning sprockets in the four corners of therectangle, vertical transfer portions being provided in parallel withthe transition portions to take care of the free end of the plates andtransfer this end from the upper part to the lower part, and vice versa,the plates being guided for parallel movement.

In another prior art moving ramp according to U.S. Pat. No. 2,893,538wherein no endless chains are provided and wherein the plates are guidedon upper and lower guide rails in the supporting and returning part,respectively, the plates are driven by means of gear wheels engagingracks on the plates in the upper part as well as the lower part. Theplates are transferred between the parts at the two ends of the movingramp by means of synchronously driven arms engaging the plates at thetwo ends thereof to transfer the plates by a parallel movement betweenthe parts.

These prior art devices necessitate a large construction height in orderthat means provided for the transfer of the plates from one part to theother at the ends of the endless chains and for advancing the plates inthe upper and lower parts will function in a satisfactory way.

If it is necessary to have the loaded part located substantially at thelevel of the supporting floor structure a substantial space must beprovided below the loaded part to receive the returning part and thedriving machinery, which means that the floor structure must form a"ditch" providing the necessary space.

SUMMARY OF THE INVENTION

The purpose of the invention is to provide a moving ramp of the kindreferred to above which allows an extremely small construction heightwhich may be less than 150 mm so that no modification at all of thesupporting floor structure is necessary and the moving ramp does notinterfere with existing space below the floor structure due to the factthat the moving ramp can be disposed directly on the floor structure. Bythis arrangement the further advantage is achieved that the moving rampcan easily be relocated should this be necessary when the room or otherpremises where the moving ramp is located have to be remodeled.

The said purpose is achieved by the moving ramp of the kind referred toabove having obtained the characterizing features of claim 1.

BRIEF DESCRIPTION OF THE DRAWING

Embodiments of the invention will be described in more detail belowreference being made to the accompanying drawings in which

FIG. 1 is a diagrammatic side view of an embodiment of the moving rampaccording to the invention,

FIG. 2 is a fragmentary cross-sectional view along line II--II in FIG.1,

FIG. 3 is a fragmentary cross-sectional view along line III--III in FIG.1,

FIG. 4 is a fragmentary view similar to FIG. 1 showing the moving rampin another functional position,

FIG. 5 is a plan view of the embodiment in FIG. 1,

FIG. 6 is an enlarged fragmentary side view of the rotating guideelement at the left-hand end of the moving ramp,

FIG. 7 is a view corresponding to FIG. 6 and shows a press-down elementcooperating with the plate,

FIG. 8 is a diagram showing the force distribution in a chain at normaloperation,

FIG. 9 is a corresponding diagram showing the force distribution in thechain in the novel drive wheel arrangement, and

FIG. 10 is a diagrammatic side view of a drive wheel device when thechain is driven according to FIG. 9.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The moving ramp comprises a number of plates 10 the upper side 11 ofwhich forms the surface for carrying goods or people to be transportedon the moving ramp. Each plate has two wheels 12 rotatably mounted tothe plate, whereby the wheel pairs utilize the same wheel track. At eachend the plate is beveled at the lower side thereof to form an inclinedsurface 13. Each plate is connected at the edges thereof at the shaft12A of one wheel pair only to two endless drive chains 14 running overturning wheels 15 indicated diagrammatically only herein. The wheels aremounted in stationary bearing means. Two upper stationary supportingrails 16 extend in parallel with each other and with the upper parts ofthe endless chains mutually spaced horizontally a distance adjusted tothe wheel track of the wheel pairs. In the same way two lower supportrails 17 are provided along the lower parts of the endless chains inparallel with the upper support rails.

At the left end of the moving ramp two rotatable guides 20 are providedon a common drive shaft which --in case of drive chains driven to movethe upper part of the moving ramp from the right to the left accordingto the arrow 21--are driven in counter-clockwise direction by means ofthe drive chains 14 via drive linkage 20A. Said guides are shaped,located and position synchronized such that they Can engage withoutjamming the trailing free wheel pair of the plate 10E which occasionallyis being carried around the turning wheels 15 at the left end of themoving ramp at the leading wheel pair thereof so that the trailing endof the plate as a consequence thereof will be positively guided whilemoving from the upper part to the lower part where the guides will againdisengage the wheels.

At the right-hand end of the moving ramp corresponding rotating guides22 are provided which are shaped in a corresponding manner as the guides20 to receive the wheels at the free end of the plate. They are drivensynchronously with the drive chains in counter-clockwise, direction bymeans of auxiliary chains 14B via drive linkage 22A to engage the plateat the right-hand free end thereof and raise the plate when it shall betransferred from the lower part to the upper part of the moving ramp sothat the plate also at the right-hand end thereof will be positivelyguided during this movement.

In the upper support rails gaps 23 must be provided to allow themovement of the wheel pair connected to the drive chains, upwards ontoand downwards from, respectively, the upper support rails. In order thatthe wheels at the trailing end of the plate at the right-hand end of themoving ramp and the leading end of the plate at the left-hand end of themoving ramp can pass over this gap when the plates are moving to theleft in the upper part of the moving ramp a rotatably mounted supportroller 24 is provided to support the plate by engaging the lower sidethereof when the plates are passing over the gaps 23 so that the platesare prevented from falling down into the gaps.

FIG. 6 discloses in more detail how the guide 20 should be constructed.The path to be described by the center of the wheel 12 on the plate 10Eat the transfer from the upper part to the lower part of the moving rampis a circle 25 having the center O₁. However, the guide 20 should rotateabout a center O₂ which is displaced to the left upwards, the angle αand the distance c being related to the radius r of the wheel 12 and theradius R of the path 25 according to the relationship

    c>R sin α

and ##EQU1## wherein α>0 and α preferably is great because lower normalforces in the mechanism are obtained as a consequence thereof. The guidesurface 26 of the guide 20 should be semicircular and it can be arrangedto engage the wheel 12 proper but it can also be arranged to engage aspecific engagement wheel provided on the wheel shaft, such as a ballbearing, having a smaller diameter than the wheel, and in that case itis of course the radius of this specific guide wheel which is the radiusr in the above relationship.

When the moving ramp is driven at high speed the mass forces will havesuch influence on the plates that these will disengage the guide 20. Inorder to eliminate this disadvantage a press-down cam 27 is provided,FIGS. 1 and 7, located on a wheel 27' the circumference of which shouldbe as large as the pitch of the plates. This means that the press-downwheel will rotate one revolution for each plate. The press-down wheelrotates in clockwise direction about the center O₃. However, the platemust be dressed down during about 1/6 only of a revolution of thepress-down wheel from the moment when the guide 20 has just engaged thewheel of the trailing end of the plate. The contour of the press-downcam should be shaped in view hereof. The wheel should not unnecessarilyengage the plate because in that case the wheel may interfere with theguide 20. Preferably, the press-down cam is coated with a soft material(rubber or polyurethane).

The guide 22 at the right-hand end of the moving ramp can be shaped in asimilar manner as shown in FIG. 6 but in this case it is not necessaryto provide a press-down cam because the wheel 12 is guided by the guiderail 17.

At the ends of the moving ramp where the procedure of transferring theplates from one part to the other takes place the moving ramp should becovered by an approach ramp 28 on which goods or persons pass onto andout from the upper load carrying part of the moving ramp.

Due to the manner in which the plates are connected to the drive chainsand are guided for transfer from one part to the other of the movingramp the distance between the parts can be kept very small so that anextremely low construction height can be imparted to the moving rampsaid height being below about 150 mm. This means that the moving rampcan be disposed on a supporting basement having flat upper side, andaccordingly it is not necessary to have this basement shaped in aspecific manner to provide space for the drive and turning machinery andfor the returning lower part of the moving ramp. By this location of themoving ramp it is also possible that the ramp can be relocated in asimple manner from one place to the other.

It is not necessary that the moving ramp extends horizontally; it canalso be inclined from one end to the other up to 10° to 12°.

As will be easily realized the rotating guides 20 and 22 and the supportrollers 24 will function in the same manner as described above butreversely in case the drive direction of the moving ramp is reversed sothat the upper part of the moving ramp is driven in a direction oppositeto the arrow 21.

If the moving ramp is driven by the sprocket wheels at one end of themoving ramp being connected to a drive motor the force distribution inthe upper part of the chains, which drives the plate in the upper loadedpart of the moving ramp will be obtained as shown in FIG. 8 wherein thegreatest stress is designated F and will be obtained at the drivensprocket wheel, the right-hand wheel in FIG. 8. This stress can beconsiderable and necessitates heavy drive chains to be provided. Suchchains have a large pitch and require large sprocket wheels because thenumber of teeth of the sprocket wheels cannot be lower than apredetermined minimum number of teeth due to the so called polygoneffect and poor engagement between the chain and the sprocket wheel.However, large sprocket wheels require a great construction height ofthe moving ramp which is contrary to the purpose of the invention.

In order to overcome this drawback several drive stations therefore areprovided along the upper part of the drive chain said stations beingdistributed along said part and each comprising for example an electricmotor, a gear and a sprocket wheel. For very long moving ramps it may benecessary to provide corresponding drive stations also for the lowerpart of the drive chains. This embodiment is shown diagrammatically inFIG. 9 wherein also the stress distribution in the chain is illustrated.If n drive stations are provided there will be obtained at a loadcorresponding to that in FIG. 8 a maximum stress in the chain, which isabout F/n. In this way the dimensioning of the drive chains will beindependent of the length of the moving ramp and it is possible tomaintain a weak chain and thus small turning wheels for all lengths ofthe moving ramp.

An embodiment of a drive station for the arrangement according to FIG. 9is shown in FIG. 10. A larger chain sprocket 29 is drivingly engagingthe upper part as well as the lower part of the drive chain 14 and shallbe connected over a gear to an electric drive motor. The upper part iskept in engagement with the sprocket wheel by means of a holding-onwheel 30 while a slide bearing 31 can provide the necessary holding-onof the lower part.

In the same way as a distribution of the stresses in the drive chains isobtained in an arrangement having several drive stations as describedabove, the acceleration and breaking forces will be distributed over thelength of the drive chains.

The drive stations can be made rather small so that they can be builtinto the balustrades commonly arranged one at each side of the movingramp.

At the ends of the moving ramp the plates when being transferred fromone part to the other will move against each other due to the fact thatthe end connected to the chains will describe a circular movement (withthe radius R). If the ends were straight a large initial spacing betweenthe plates would be necessary which is unsuitable from the securitypoint of view considering the risk of people being caught. By thisplates being beveled at 13, FIG. 1, the initial spacing between theplates can be reduced considerably. If the spacing is designated S₀ andthe height of adjacent surfaces of the plates is designated h thefollowing relationship can be established: ##EQU2## If R=32 mm and h=32mm there will be obtained S₀ ≧6 mm while in the case of h being instead10 mm (beveled plate) S₀ ≧1 mm.

In a known manner the plates can form interengaging teeth or fingers atthe ends thereof.

I claim:
 1. Moving ramp comprising plates, wheels on said platessupporting the plates, stationary guides forming upper and lower runwaytracks for the wheeled plates, guiding said plates for movement at anupper level to form the loaded part of the moving ramp, and at a lowerlevel which is substantially parallel with the upper level, to form thereturning part of the moving ramp, adjacent plates in each part beingclosed to each other, endless chains extending along said parts, theplates at the edges thereof being pivotally connected to the endlesschains at one end of the plates, the other end of the plates being freefor angular adjustment, a sprocket wheel for each chain at each endthereof, a rotating element forming a guide for lowering and raising,respectively, said other end of the plates along a circular path ofmovement, for displacement of said plates in a substantially horizontalposition one at the time from one part to the other, means for drivingsaid rotating element synchronously with the sprocket wheel, therotation center of each of the rotating elements being displacedobliquely upwards toward the adjacent end of the moving ramp in relationto the center of the circular path of movement of said other end of theplates, and a plurality of drive stations for the endless chains fordriving the chains.
 2. Moving ramp as in claim 1 wherein the upperrunway track forms a gap to allow the passage of the wheels through thetracks at the end of the plate connected to the endless chains. 3.Moving ramp as in claim 2 wherein means are provided for supporting theplates by engaging the lower side thereof at the movement of the plateover the gap.
 4. Moving ramp as in claim 1 wherein the displacement (C)of the center of the rotating element at an angle (α) to the horizontalplane is defined by the relationships

    c>R sin α

and ##EQU3## wherein R is the radius of said circular path of movement,and r is the radius of the wheels of said plates.